实现静态nsOutlineView

我很难收集到足够多的知识片段来实现一个静态的、永不改变的NSarray中定义的结构的nsOutlineView。 This link 已经很好了,但它不能帮助我掌握子菜单。我想它们只是嵌套的NSarray,但我不清楚。

假设我们在一个NSARRAY中有一个NSARRAY,定义为

NSArray *subarray = [[NSArray alloc] initWithObjects:@"2.1", @"2.2", @"2.3", @"2.4", @"2.5", nil];
NSArray *ovStructure = [[NSArray alloc] initWithObjects:@"1", subarray, @"3", nil];

文本在OutlineView:ObjectValueForTableColumn:ByItem:中定义。

- (id)outlineView:(NSOutlineView *)ov objectValueForTableColumn:(NSTableColumn *)tableColumn byItem:(id)ovItem
{
    if ([[[tableColumn headerCell] stringValue] compare:@"Key"] == NSOrderedSame)
    {
        // Return the key for this item. First, get the parent array or dictionary.
        // If the parent is nil, then that must be root, so we'll get the root
        // dictionary.

        id parentObject = [ov parentForItem:ovItem] ? [ov parentForItem:ovItem] : ovStructure;

    if ([parentObject isKindOfClass:[NSArray class]])
        {
            // Arrays don't have keys (usually), so we have to use a name
            // based on the index of the object.

        NSLog([NSString stringWithFormat:@"%@", ovItem]);
            //return [NSString stringWithFormat:@"Item %d", [parentObject indexOfObject:ovItem]];
        return (NSString *) [ovStructure objectAtIndex:[ovStructure indexOfObject:ovItem]];
        }
    }
    else
    {
        // Return the value for the key. If this is a string, just return that.

        if ([ovItem isKindOfClass:[NSString class]])
        {
            return ovItem;
        }
        else if ([ovItem isKindOfClass:[NSDictionary class]])
        {
            return [NSString stringWithFormat:@"%d items", [ovItem count]];
        }
        else if ([ovItem isKindOfClass:[NSArray class]])
        {
            return [NSString stringWithFormat:@"%d items", [ovItem count]];
        }
    }

    return nil;
}

结果是'1'、'('(可展开)和'3'。nslog显示以“(”开头的数组,因此是第二个项。扩展它会导致崩溃,因为超出了界限。我尝试使用parentforitem:但无法找到将结果与之进行比较的方法。

我错过了什么?